Research by Harvard Medical School faculty at the Dana Farber Cancer Institute may shed light on a new strategy to fight HIV, a virus which causes AIDS. Experiments performed in the test tube show a new combination yields positive results.

The study appearing in the December 1 issue of the Proceedings of the National Academy of Sciences showed that a mixture of two drugs--pentoxifylline and Ro24-7429--was 100 times more effective than either drug alone at blocking the function of "Tat," a viral protein essential to the spread of HIV in the body.

By inhibiting Tat, the scientists conducting the study sought to prevent HIV from reproducing itself after it has infected a cell.

"After [the virus] establishes itself in a host cell, then it starts making its own proteins," said Debajit K. Biswas, the principal author of the paper, who is a researcher at the Dana Farber and lecturer at the Medical School. "We are trying to affect virus replication."

In their study, the researchers inserted genes from HIV into human T cells (the cells normally infected by the virus) and tested the ability of drugs to block the action of these essential genes.

The next step, according to Biswas, is to test the two drugs on T cells that are infected with live HIV. If those tests show positive results, then it may be possible to eventually test the drugs on human patients.

Biswas believes the method shows promise because it targets specific viral genes. In the past, this class of drugs has proven to be too toxic for use in human patients. But, according toBiswas, "The side effects can be avoided by usingvery low concentrations of these drugs [incombination]."

Dr. Powel H. Cazanjan, assistant professor ofmedicine and director of the AIDS program at theBrigham and Women's Hospital said in a phoneinterview yesterday that while there has beenexperimental evidence to support the effectivenessof other drugs to block the Tat protein, "so farthe clinical experience with tat inhibitors hasnot been fruitful."

But Cazanjan said this type of strategy isworthy of further study. "I think it's an area ofpromise, and like other areas it is worthinvestigating clinically," he said